The aim of our program is to study the role of nonhistone chromosomal proteins in the regulation of gene expression during the cell cycle, a problem central to understanding the control of growth, development, differentiation, and neoplasia. These studies are predicated upon previous findings from our laboratory which revealed differences in the nonhistone chromosomal proteins synthesized and associated with the genome at various times during the cell cycle and a series of chromatin reconstitution studies which indicated that nonhistone chromosomal proteins are responsible for mediating the differences observed in the transcriptional capacities of S phase and mitotic chromatin. During the first year of this grant, we have focused on the involvement of nonhistone chromosomal proteins in the control of histone gene transcription. Initially, we synthesized a DNA complementary to histone messenger RNA sequences and utilized this high resolution probe to demonstrate: a) histone messenger RNA sequences are present in the polysomal RNA during S phase but not during the G1 phase of the cell cycle; b) histone messenger RNA transcription is restricted to chromatin from S phase cells; and c) S phase nonhistone chromosomal proteins dictate the availability of histone genes for transcription. During the next year we intend to pursue two primary objectives. First, the histone mRNA will be fractionated into the five individual components--those which serve as templates for F2a1, F2a2, F2b, F3 and F1. The fractionated histone messages will each then be polyadenylated and used to prepare cDNA's. The methodology for preparation of the cDNA's will be that which we utilized for the synthesis of the cDNA to total histones mRNA's. The cDNA's will then be used to study a) the role of cell cycle stage-specific nonhistone chromosomal proteins in regulating the transcription of the individual histone genes and b) the in vivo processing of histone gene transcripts in the nucleus, as well as in the cytoplasm.